That's the point of both the flow meter and ball valve. Using two ball valves would be optimal but even one on the line going to the UV
would be fine. Any excess flow that the ball valve restricts on the UV
line would go to the tank and not cause any back pressure on the pump.
Still need to know the wattage on the UV
. As I said before if it's a 36W then the flow isn't too fast and you don't need any additional plumbing.
If it's 9 or 18 watts then flow should be closer to 200-300 GPH
through the UV
for it to be affective.